Frequency divider



pril 8, 1947. B. BAUER FREQUENCY DIVIDER Filed April 11, 1944 M InINVENTOR.

L. 5 Bauer BY p A TTOR/VE Y Patented Apr. 8, 1947 FREQUENCY DIVIDER L.Brunton Bauer, Palo Alto, Calif., assignor to Hewlett-Packard Company,Palo Alto, Calif., 21. copartnership consisting of William R. Hewlettand David Packard Application April 11, 1944, Serial No. 530,503

4 Claims.

This invention relates generally to electrical apparatus for producing afrequency of known value from a higher given frequency. Moreparticularly it relates to so-called frequency dividers suitable forproducing frequencies which can be used as standards for test purposesand the like. It is an object of the invention to provide apparatus ofthe above character which has a high degree of stability with respect tothe desired output frequency.

Another object of the invention i to provide a frequency divider ofsimple construction which can be used to produce currents of frequenciesover a wide range, including frequencies ranging from say '10 kilocyclesto 100 cycles per second. A further object of the invention is toprovide a frequency divider in which division by numbers other thanintegers is possible, that is one with which any desired ratio may beobtained as distinguished from prior art dividers which are limited toobtaining frequencies having an integralrelation with the drivingfrequency.

Further. objects of theinvention will appear from the followingdescription in which the preferred embodiment of the invention has beenset forth in detail in conjunction with the accompanying drawing,

The frequency divider illustrated in the drawing is adapted to beexcited from a suitable oscillator I0, and is adapted to deliver a givenlower frequency tothe output or load I I. The oscillator can be of theelectronic type preferably with a crystal control to maintain itsfrequency constant. The frequency divider consists of a pair of vacuumtubes I2 and It, with tube I2 arranged to operate as a modulator withhigh amplification gain, and with tube l3 arranged to operate also as amodulator. Under certain conditions it may be desirable to also operatetube l3 with considerable distortion to act as a frequency multiplier.Both ofthe'se tubes are preferably of the 'pentagrid type, known bymanufacturers specifications as No. 6L7. Thus each tube is shownprovided with plate P, cathode K, and grids Gl, G2, G3, G4 and G5. GIand G3 are control grids, G2 and G4 are screen grids, while G5 is asuppresser grid.

In :order to form suitable input and output circuits for the modulatortube 12, cathode K together with the suppressor grid G5 are connected tothe grounded conductor I4, through the biasing resistor Hi. Thisresistor is shunted by bypass condenser IT. The control grid GI isconnected to ground through the biasing resistor I5, and is coupled tothe oscillator Ill through the variable resistor I8 and condenser I9.Control grid G3 of tube I2 is also connected to biasing resistor 2|, andis coupled to the plate of the tube I3 through condenser 22.

The plate circuit or output of tube I2 is tuned by the inductance 23,which is shunted by condenser 24. One side of inductance 23 connects tothe plate P of tube I2, while the other side connects with the load I Iand plate current source 25 through conductor 26. Transfer of energy tothe load I I occurs through the coupling condenser 27.

The cathode K of tube I3 likewis connects to grounded conductor 28through the biasing resistor 29, which is shunted by by-pass condenser3I. Control grid GI is connected to ground through the biasing resistor32, and is preferably directly coupled with the oscillator Ill throughthe variable condenser 33, resistor I8 and condenser l9. Control grid G3is connected to grounded conductor 28 through the biasing resistor 34,and is coupled through condenser 36 to the plate P of tube I2. Conductor23 connects with the screen grids G2 and G4, of both tubes, through theresistors 3'! and 38. An additional biasing resistor 39 connects thescreen grids of tube I3 to ground. The screen grids of both tubes arealso connected to ground through the by-pass condensers M and G2.

The plate circuit or output of the tube I3 is tuned to a given frequencyby the inductance 43 which is shunted by condenser 44. Conductor 45connects one side of the inductance to the plate P of tube I3, while theother side of the inductance connects with conductor 25.

The biasing resistors and plate voltages for the tubes I2 and I3 areselected and adjusted so that tube i2 operates as a modulator with highamplification gain. Tube I3 may be adjusted to operate with considerablyless amplification gain. Under certain conditions of operation,particularly where n is an integer, it is desirable to adjust tube I3for a substantial amount of distortion, whereby it also operates as afrequency multiplier.

15 kilocycles.

3 The frequency delivered to the load I! must be f where is thefrequency of the oscillator Ill. The filter formed by inductance 23 andcondenser 24, is tuned to this frequency The filter formed by inductance43 and condenser 44 is tuned to the frequency Assuming for example thatthe oscillator I operates at a frequency of 100 kilocycles and that ancycles are therefore fed back regeneratively from the output of tube I3to the control grid G3 of tube l2, through the coupling condenser 22.

Assuming that the apparatus is in operation, currents at the frequencyof 100 kilocycles are supplied by the oscillator II] to the control gridGI of the modulator tube l2. In this modulator the frequency of 100kilocycles is mixed with the frequency of 85 kilocycles or 115kilocycles being fed back from the plate circuit of tube i3, aspreviously described, whereby there is produced a, differentialfrequency of 15 kilocycles. Currents at this frequency are supplied tothe load II, and they are also applied to the control grid G3 of themodulator tube l3, through the coupling condenser 36. Control grid GI ofthis modulator is also supplied with current directly from theoscillator 10 through coupling condenser 33,

thus causing production of a differential frequency of 85 kilocycles, towhich the output of tube I3 is tuned. This as previously explained isthen supplied to the input of modulator tube 12 to coupling condenser22, to beat with the frequency of 100 kilocycles to produce the desiredProduction of the desired differential frequency of 85 kilocycles or 115kilo- ,cycles in the output of tube I3 is also intensified because ofthe distortion for which the tube is adjusted.

No difiiculty is encountered in starting the ap-' paratus in operationbecause initial transient pulses are quickly built up by theregenerative action. The regenerative action is not to be confused withregeneration capable of sustained generation of oscillations, becausewhen the supply of current from the oscillator I0 is interrupted thesupply of current at 15 kilocycles or immediately stops.

Assuming that the oscillator Ill is designed to maintain a desiredfrequency, then my frequency divider is capable of producing a lowerfrequency of constant value and sinusoidal wave form which can be,usedas a standard for test purposes and the like. Should one desire toproduce currents .at two or more frequencies differing from each otherby say multiples of 10, a number of such frequency dividers can beprovided with currents from the output of one divider serving to supplyexciting current to a succeeding divider. In this manner frequencies canbe supplied in steps ranga. pc ing from say 10 megacycles per second ormore to cycles per second or less.

A particular feature of the invention is that it makes possible divisionby numbers other than integers, thereby making it possible to obtain anydesired ratio. Dividers previously employed have been limited in thisrespect and have permitted one to obtain only frequencies having anintegral relation to the driving or exciting frequency.

I claim:

1. In electrical apparatus for producing a desired fixed frequency, apair of electronic devices, the first arranged to operate as a modulatorwith substantial amplification gain, and the second arranged to operateas a frequency multiplier, means for supplying current of fixedfrequency f to the modulator, means for supplying current of .thefrequency from the frequency multiplier to the modulator, means forsupplying current of the frequency from the modulator to the frequencymultiplier and for supplying current of such frequency to the input ofthe second modulator, where 1': is a number which may or may not beaninteger, means for tuning the output of the secondmodulator to thefrequency I and for supplying current at such frequency to the input ofthe first modulator, and means for supplying current at the frequency fdirectly to the input of the second modulator.

3. In electrical apparatus for producing a desired fixed frequency, apair of electronic modulators each having input and output circuits, thefirst modulator being arranged for high amplification gain and thesecond modulator being arranged to have lesser amplification gain 'andacting as a frequency multiplier, means for supplying current of fixedfrequency f to theinput of the first modulator, means for tuning theoutput of the first modulator to the frequency and for supplying currentof such frequency to an output load and to the input of the secondmodulator, means for tuning the output'of the second modulator to thefrequency a and for feeding back current of suchfrequency to the inputof the first modulator, and means for supplying current at the frequency1 directly to the input of the second modulator.

4. In electrical apparatus for producing a, desired fixed frequency, apair of electronic modulators, means for supplying current of fixedfrequency f to both the first and second modulators, means for supplyingcurrent of a frequency from the second modulator to the first modulator,where n is a number which may or may not be an integer, and meansserving to supply current of the frequency n from the first modulator tothe second modulator and to a load output.

L. BRUNTON BAUER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

